Electrode cooling device

ABSTRACT

Electrode holder with an electrode cooling device on its underside, said electrode cooling device being electrically insulated from the electrode holder in order to avoid damage by arcing. To improve the protection of the electrode holder, the cooling device essentially covers the underside of said holder. To improve the spray cooling, the nozzles are equipped with a compressed air supply.

It is known to cool the graphite electrodes of arc furnaces by sprayingcooling water against the surface of the electrodes. For this purpose,arranged underneath the electrode holder attached to the electrodecarrying arm is a spray ring, which is formed by a tube to which coolingwater is admitted and directs spray nozzles toward the surface of theelectrodes. The cooling has the effect of reducing the electrodeconsumption and also protecting the clamping devices for the electrodefrom excessive heat exposure. The known arrangement has the disadvantagethat electric arcs which may damage both the cooling device and theelectrode holder can occur. This applies in particular if the electroderuptures; there is then the risk of the electrode holder settling on thestump of the electrode connected to the bath. The same may happen ifthere are remains of scrap on the furnace.

According to the invention, these disadvantages are reduced oreliminated by the electrode cooling device being electrically insulatedfrom the electrode holder. As a result, not only the cooling device butalso the electrode holder are protected. This protection of theelectrode holder can be improved in comparison with a conventionalarrangement of the cooling device by the electrode cooling deviceessentially covering the underside of the electrode holder. It is formedwith a large surface area and is given an outer contour which is similarto or the same as that of the electrode holder (seen from below). It canbe fastened to fixed parts of the electrode holder. It may projectfreely under the movable parts of the electrode holder or—moreexpediently—be supported on them in such a way that the clampingmovements of these parts do not impair the support.

For the connection or support of the electrode cooling device on theelectrode holder, releasable fastening devices must be provided. Inorder that effects of the furnace do not render them unusable, theyshould be arranged above cooled parts of the electrode cooling device.They are expediently accessible from the side.

Furthermore, the invention seeks to improve the cooling action of thespray nozzles. For this purpose, a compressed air supply is provided onthe spray nozzles, providing better distribution and possibly alsoalignment of the cooling water with the parts to be cooled. The coolingis made more effective as a result and the consumption of cooling mediumis lowered. Thanks to the better distribution, adequate cooling can alsobe maintained if one or other of the spray nozzles should happen tofail. If need be, this feature is worthy of protection independently ofthe claims to which reference is made.

The failure of nozzles caused by splashes can be prevented according tothe invention by a shield which covers the direct spraying directionfrom the bath or arc to the nozzles being provided underneath thenozzles.

The invention is explained in more detail below with reference to thedrawing, which illustrates an advantageous exemplary embodiment and inwhich:

FIG. 1 shows the side view of an electrode holder with a cooling device;

FIG. 2 shows the underside of the electrode holder and cooling device;

FIG. 3 shows a partial section along section line A-A of FIG. 1;

FIG. 4 shows the detail “X” indicated in FIG. 1; and

FIG. 5 shows the detail “Y” indicated in FIG. 4.

Fastened to the front end 1 of an electrode arm by means of flanges 2 isthe electrode holder 3, which comprises a rear, shaft-like part 4, fixedclamping jaws 5 connected to said part and a movable clamping jaw 6.This arrangement is of a conventional type and is provided with suitabledrive and coolant supply lines.

Arranged underneath the electrode holder 3 is the cooling device 10formed according to the invention, which has the outer shape of ahorizontal plate, the outline of which is essentially the same as thatof the electrode holder 3, as FIG. 2 shows in particular. In its frontregion, it forms an annular part 11, which encloses the electrode 12.

The cooling device is a flat, hollow box, which is formed by a lowerwall 14, an upper wall 15 and a surrounding outer wall 16. In the regionof the annular part 11 there is also an inner wall 17. At the rear end18, the box is likewise closed by a suitable wall and connected by meansof a line 19 to a cooling water source.

The cooling device 10 is connected to the fixed part 4 of the electrodeholder by four fastening devices, which are indicated generally in FIG.2 by the reference numeral 20. Corresponding fastening devices may alsobe provided for the fixed clamping jaws 5. Their construction isrepresented more precisely in FIG. 3. Attached to the lower plate 21 ofthe electrode holder are studs 22, each of which reaches with itsportion 23 into a depression 24 in the cooling device 10 and is securedthere by means of a bolt 25, to be fitted from the side. The head of thebolt 25 sits in a depression, which is protected by means of a plate 26which is releasably fastened in a suitable way.

The stud 22 is electrically insulating. For example, it may consistcompletely of electrically insulating material. In the examplerepresented, it comprises a first plate 30, welded to the lower plate22, an insulating plate 31 and a stud plate 32 screwed thereto, thescrews 33 being electrically isolated from the stud plate 32 byinsulating inserts 34. This has the effect that the cooling device 10 iselectrically isolated from the electrode holder. It goes without sayingthat the cooling water supply line 19 is also correspondingly insulated.

The annular part 11 of the cooling device may protrude freely from therear part of the cooling device, held by means of the fastening devicesjust explained. It is better if it is additionally supported on themovable parts of the holder 6. Provided for this is a device 35, whichis represented in more detail in FIG. 4. Protruding downward from theclamping jaw 6 is a support 36, which ends in an insulating plate 37.Fastened on the upper side of the part 11 of the cooling device is asliding plate 38, which bears against the insulating plate 37. Theelectrode terminal 6 can move freely over this supporting device withinthe predetermined range without losing the supporting effect.

An additional insulation of the contact jaws can have the effect thatdust does not cause bridging.

The cooling device acts as a heat protecting plate for the electrodeholder and in this way can increase its service life significantly. Itcan easily be retrofitted on existing holders. Since the assembly screws25 are protected and it is ensured in this way that they remainoperational, rapid and speedy assembly and disassembly can be expected.

To make it possible if desired for the cooling device to be provided fora fitted electrode, it may be provided that the annular part 11 of thecooling device is formed in a divided manner.

The annular part 11 of the cooling device is formed such that it ishollow in a manner similar to its rear part. Arranged in the wall 17 arenozzle bores 40, through which the pressurized cooling water located inthe interior space 41 of the cooling device is sprayed out against thesurface of the electrode 12. Opening out obliquely into the bore 40 is abore 42, which extends from a compressed air line 43, which is weldedonto the inner periphery of the wall 17 alongside the row of spray bores40. It is connected in a way not represented to a compressed air supplyline 44 (FIG. 1), which is connected to the cooling device 10 in anelectrically insulating manner.

The compressed air supply to the spray nozzles 14 assists thedistribution of the cooling water and the formation of the spray jet.The surface of the electrode is wetted better and the cooling action iscorrespondingly increased.

FIG. 5 reveals that the lower wall 14 protrudes inwardly at the innerperiphery of the annular part 11 of the cooling device more than thewall 17. As a result, the mouth of the spray bore 40 is shielded betterin the downward direction and protected from splashes which could leadto blocking.

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 21. An electrode assembly comprising an electrode holder foran electrode and an electrode cooling device arranged underneath saidelectrode holder and comprising cooling-water spray nozzles having boresand being directed at the electrode, characterized in that the nozzlesare equipped with a compressed air supply.
 22. The electrode assembly asclaimed in claim 21, characterized in that the compressed air supplyopens out into the bores of the spray nozzles.
 23. The electrodeassembly as claimed in claim 21, characterized in that a row of spraynozzles is arranged on or in a wall of the cooling device and connectedto the wall along this row is a compressed air line, from whichconnecting bores lead to the bores of the spray nozzles.
 24. Theelectrode assembly as claimed in claim 21, characterized in that thespray nozzles have openings and a shield which covers the directspraying direction from a bath or an arc to the openings is providedunderneath the openings of the spray nozzles.
 25. The electrode assemblyas claimed in claim 24, characterized in that, underneath the spraynozzles, the cooling device comprises a wall which runs transversely inrelation to the direction of the electrode and an edge of whichprotrudes further toward the electrode than the nozzles, to form theshield.
 26. The electrode assembly as claimed in claim 21, characterizedin that the electrode cooling device is electrically insulated from theelectrode holder.
 27. The electrode assembly as claimed in claim 21,characterized in that the electrode cooling device essentially coversthe underside of the electrode holder.
 28. The electrode assembly asclaimed in claim 21, characterized in that the electrode cooling deviceis fastened to fixed parts of the electrode holder and is supported on amovable part of the electrode holder.
 29. The electrode assembly asclaimed in claim 21, characterized in that releasable fastening andsupporting elements for the electrode cooling device are arranged abovecooled parts of the same.
 30. The electrode assembly as claimed in claim29, characterized in that the releasable fastening and supportingelements are accessible from the side.
 31. The electrode assembly asclaimed in claim 22, characterized in that a row of spray nozzles isarranged on or in a wall of the cooling device and connected to the wallalong this row is a compressed air line, from which connecting boreslead to the bores of the spray nozzles.
 32. The electrode assembly asclaimed in claim 22, characterized in that the spray nozzles haveopenings and a shield which covers the direct spraying direction from abath or an arc to the openings is provided underneath the openings ofthe spray nozzles.
 33. The electrode holder as claimed in claim 23,characterized in that the spray nozzles have openings and a shield whichcovers the direct spraying direction from a bath or an arc to theopenings is provided underneath the openings of the spray nozzles. 34.The electrode assembly as claimed in claim 31, characterized in that thespray nozzles have openings and a shield which covers the directspraying direction from a bath or an arc to the openings is providedunderneath the openings of the spray nozzles.
 35. The electrode assemblyas claimed in claim 22, characterized in that the electrode coolingdevice is electrically insulated from the electrode holder.
 36. Theelectrode assembly as claimed in claim 23, characterized in that theelectrode cooling device is electrically insulated from the electrodeholder.
 37. The electrode assembly as claimed in claim 24, characterizedin that the electrode cooling device is electrically insulated from theelectrode holder.
 38. The electrode assembly as claimed in claim 25,characterized in that the electrode cooling device is electricallyinsulated from the electrode holder.
 39. The electrode assembly asclaimed in claim 22, characterized in that the electrode cooling deviceessentially covers the underside of the electrode holder.
 40. Theelectrode assembly as claimed in claim 23, characterized in that theelectrode cooling device essentially covers the underside of theelectrode holder.